The present invention relates to the fabrication of semiconductor integrated circuits (IC""s). More particularly, the present invention relates to an improved apparatus and method for lifting a substrate from the surface of a work piece holder subsequent to a processing step.
During the manufacture of a semiconductor-based product, for example, a flat panel display or an integrated circuit, many processing steps are employed. Broadly speaking, the manufacturing process involves placing a substrate into a process chamber, processing the substrate (e.g., etching or depositing) and removing the substrate from the process chamber.
It has been found that a sticking force is often times encountered between the substrate and the surface of a chuck that causes the substrate to stick to the surface of the chuck when the time comes to remove the substrate subsequent to the processing step. By way of example, a sticking force may be encountered when the chuck is used as an electrostatic device to hold a substrate during processing. To facilitate discussion of this problem, FIG. 1 depicts an exemplary prior art lifting arrangement 100. Lifting arrangement 100 includes a work piece holder 110 (e.g., a chuck) and a lifting pin 120. Work piece holder 110 is typically designed to hold substrate 130 during processing (e.g. electrostatically). Lifting pin 120, typically disposed through the middle of the chuck, is used to move substrate 130 from the surface of work piece holder 110 to a predefined height where substrate 130 may then be lifted off lifting pin 120 and removed from the process chamber. Typically, lifting pin 120 is placed in the center of work piece holder 110 to accommodate side-swinging transport arms that are used to remove the substrate from lifting pin 120.
Often times, an electrostatic force will be built up between the chuck (or work piece holder) and the substrate during substrate processing. This may arise because of a residual charge (e.g., due to uncompensated DC bias and/or charge accumulated on the chuck surface or on the substrate). Typically, the residual charge creates an electrostatic force, which will herein be referred to as a residual holding force, between the chuck and the substrate that tends to cause them to stick to one another.
Generally, the charge that creates the residual holding force may gradually be bled away from the chuck to reduce the residual holding force and allow the substrate to be lifted off the chuck by lifting pin 120. However, this method of lifting the substrate is time-consuming since a non-trivial time constant is typically involved, and thereby disadvantageously reducing the throughput of the plasma processing system (e.g., reducing the number of substrates that can be processed by a given plasma processing system per unit of time).
If the residual charge is inadequately bled, the use of the center pin to lift the substrate off the chuck often gives rise to other problems. By way of example, the substrate may be unbalanced on the center pin (as shown in FIG. 1) because a moment is created at the point of lift, which causes the substrate to tilt. Additionally, the substrate may wobble on the center pin as it is lifted, possibly causing the substrate to fall off the center pin or wander about the center pin so that the substrate is no longer aligned on the center pin.
The aforementioned problem of substrate tilting, wobbling or wandering may be addressed in part by employing perimeter pins to lift the substrate off the chuck. FIG. 2 shows a lifting arrangement 200 that uses perimeter pins to lift the substrate. Lifting arrangement 200 includes a chuck 210 and perimeter pins 220. Also included in FIG. 2 is a substrate 230. Since the pins are distributed about the perimeter of the substrate, the aforementioned wobbling or tilting problem is substantially eliminated. However, the perimeter pin arrangement is limited in that such an arrangement cannot be used in systems that employ swinging or arcing transport arms because the perimeter pins interfere with the movement of the transport arm (e.g., the transport arm cannot clear the perimeter pins).
In view of the foregoing, these are desired, improved methods and apparatuses for lifting a substrate off a surface of a chuck in a plasma processing system without inducing substrate tilting or wobbling or interfering with the movement of a transport arm.
The invention relates, in one embodiment, to an apparatus for lifting a substrate from a surface of a chuck subsequent to a processing step. The apparatus includes a perimeter pin for lifting the substrate from the surface of the chuck to a first position wherein the substrate is disposed on the perimeter pin during lifting. The perimeter pin is configured to overcome a holding force at an interface of the substrate and the surface. Generally, the holding force is generated between the substrate and the surface during the processing step. The apparatus further includes a center pin for moving the substrate from the first position to a second position wherein the substrate is disposed on the center pin during moving. The second position is further away from the surface of the chuck than the first position.
The invention relates, in another embodiment, to a substrate processing system. The system includes a work piece holder arrangement that is configured to remove a substrate from a surface of the work piece holder when the substrate is coupled to the surface of the work piece holder by a holding force. Further, the work piece holder includes a first pin configured to break the holding force between the substrate and the work piece holder by lifting the substrate from the surface to a first position. The substrate is disposed on the first pin during lifting. The work piece additionally includes a second pin for moving the substrate from the first position to a second position wherein the substrate is disposed on the second pin during moving. The second position is further away from the surface of the work piece holder than the first position.
The invention relates, in yet another embodiment, to a method of removing a substrate from a surface of a work piece holder in a substrate process chamber. The method includes producing a holding force between the substrate and the surface during processing. The method further includes breaking the holding force by lifting the substrate away from the surface to a first position, the lifting is accomplished by a first pin wherein the substrate is disposed on the first pin during breaking. Thereafter, the method additionally includes moving the substrate with a second pin from the first position to a second position. The second position is further away from the surface of the work piece holder than the first position.
These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures.